import pdb
import heapq as h

# HEAP
# Insert O(log n)
# Delete O(log n)
# Search O(n)
# Building a Heap O(n)

def meetingRooms2(intervals=[[0,30],[5,10],[15,20]]):
	if (intervals == None or len(intervals) == 0):
		return 0
	# start 0, end 1
	intervals.sort(key=lambda list: list[0])
	minHeap = []
	h.heappush(minHeap, (intervals[0][1]))

	for i in range(1, len(intervals)):
		curr = intervals[i]
		earliest_end = h.heappop(minHeap)

		if (curr[0] >= earliest_end):
			earliest_end = curr[1]
		else:
			h.heappush(minHeap, curr[1])

		h.heappush(minHeap, earliest_end)


	return len(minHeap)

print meetingRooms2()